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YAML: syntax basics

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Do you know how to handle YAML strings with leading zeros? As you can see is not stored as string '' in the ordereddict, but why does yaml. First of all, there are no YAML strings, there are collections mappings and sequences and scalars.

In the normal case of loading a YAML document, a quoted scalar will be loaded as strings, and the plain scalar is open for interpretation as a special type depending on its "content". That interpretation could lead to it being a boolean, a date, a floating point value. If none of those match, the plain scalar is loaded as a string.

The normal loading case applies the Core Schema. That schema is a superset of the JSON schema, and in both plain scalars consisting of numbers only are supposed to be loaded as integers. So this answers your first question on how to handle "YAML strings". Although it loads as an integer, it is actually a subtype of the integer class, which includes information about the format of the integer i. If your YAML document is under revision control, it is nice that these kind of things don't change just because you updated some other part of the document.

This should answer your second question asking why ruamel. PyYAML doesn't do this and neither does ruamel.

xacro load yaml

Do I know how to handle '"yaml strings" with leading zeros', No I don't, but I give you you several options to select from, depending on the purpose with which you load your document just to be clear: I am the author of ruamel.

In the default, round-trip mode, I load them as things that behave like integers, but preserve outer appearances specific for the input, as YAML provides an unendless number of ways to present any specific number like 5. An alternative for that would be to unload the integer-matching regular expression from safe or round-trip mode, but that is more complex.

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xacro load yaml

Anthon Active Oldest Votes. So this answers your first question on how to handle "YAML strings" ruamel. Anthon Anthon Sign up or log in Sign up using Google. Sign up using Facebook.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.

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Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. Xacro is an XML macro language. With xacro, you can construct shorter and more readable XML files by using macros that expand to larger XML expressions. Python CMake Shell. Python Branch: noetic-devel. Find file. Sign in Sign up. Go back. Launching Xcode If nothing happens, download Xcode and try again.

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Xacro has been extended quite a bit the past year with some nice features thanks for that! But the tutorial s mostly Using Xacro to Clean Up a URDF File seem to be lagging behind, so it can be hard to figure out the exact syntax sometimes for some of these new things.

Is there a specific 'safe sub set' defined for the Python clauses? I seem to remember some discussion about that, but am not sure if that got implemented or not. I'm specifically thinking about circumventing the 'single-evaluation' limitation that still exists, right? All python expressions are allowed, except loading of new modules. What do you mean by "single-evaluation" limitation? An expression is only evaluated, when needed. This might be multiple time, e. I'm probably not fully up-to-speed, so if this is possible right now, please do tell me.

I'm sorry for the very delayed answer, gavanderhoorn. I don't seem to get emails from github Hopefully you already figured out, how to solve your issues. However, you don't need them anymore. Within the python expression you can access all your xacro properties directly via their name. Do you think, this is sufficient?

ruamel.yaml (yaml 1.2)

I think an advanced tutorial would be very beneficial for and much appreciated by the ROS community! I will help to fill the gaps as best as I can. Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up.

xacro load yaml

New issue. Jump to bottom. Copy link Quote reply. This comment has been minimized. Sign in to view. All python expressions are allowed, except loading of new modules ok, good to know. Is that explicitly stated somewhere?No API documentation available. Please see this page for information on how to submit your repository to our index. With xacro, you can construct shorter and more readable XML files by using macros that expand to larger XML expressions. It is heavily used in packages such as the urdf.

See for example, this tutorial for how xacro is used to simplify urdf files. See herefor an example showing the use of the advanced features python evaluation, yaml integration introduced in Jade. Use of new features on Indigo Many of the features highlighted as "New in Jade" below are also accessible from Indigo. To use them, the --inorder flag is required.

PyYAML yaml.load(input) Deprecation

This flag is discussed belowand for some background information see this pull request. Put simply, this flag is used to trigger Jade-enabled xacro processing on Indigo. The remainder of this document describes the features of xacro.

Both use the property tag to define values. Property tags cannot be declared inside of a xacro:macro.

xacro load yaml

New in Jade : Properties are local if defined inside of a xacro:macro. See Local properties. Currently, basic arithmetic and variable substitution is supported. This allows for more complex arithmetic expressions. Functions and constants from the python math module e.

This is useful for things like configurable robots or loading different Gazebo plugins. Define macros with the macro tag, and specify the macro name and the list of parameters. The list of parameters should be whitespace separated. They become macro-local properties. Note that "origin" is starred. This indicates that origin is a block parameter instead of a simple text parameter.

Instead, origin refers to the first element inside the "pose" block, in this case. The double-starred version "content", "anothercontent" allows to insert an arbitrary number of elements that are passed within elements subsequently available "container", "another" respectively in the example above.

The outer macro will be expanded first, and then the inner macro will be expanded. They are considered to be related to the macro e. If you want to keep a comment in the final document, separate it with an empty line from the macro. New in Jade Often, you need to pass external variables into local macro params as above for x. The pipe indicates to use the given fallback if the property is not defined in outer scope. Local properties New in Jade Properties and macros defined within a macro are local to this macro, i.

New in Jade : Relative filenames are interpreted relative to the currently processed file. Note : When including files within a macro, not the macro-defining but the macro-calling file is the one that processes the include!I haven't experimented much here and I'll update this when I do try it tomorrow, but it seems like the documentation says only the other direction is possible: values can be set on the parameter server from within a launch file, and the local copies of those values can be used inside that same launch file and used as arguments, but there is no read access to the parameter server?

I'm not sure this is possible. You may get better answers if you elaborate on why you want to do this. I'd like to have a centralized place the yaml file defining critical robot dimensions, then pass these into a xacro file defining the robot, but also allow certain nodes to get some of the same dimensions from the parameter server.

You can do some pretty complex things with this, especially when you combine it with the other new features xacro gained. I hadn't heard about that so I'm now subscribed to the xacro wiki page. I don't know. Both have their dis advantages.

I think the better solution here is for any node that needs the dimensions of the robot should pull them from the URDF that's already on the parameter server, or from one of the static transforms that's published based on the URDF. I agree. Traversing the urdf data structure to find a dimension seems like a lot of work compared to using the input dimension from the source. It can be an error check to define a value, create something from it, and then measure it again as opposed to using the original.

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Check out the FAQ! Hi there! Please sign in help. How to pass parameters loaded from a yaml file into a xacro? How did you end up solving this? Did you find a satisfactory solution? There have been earlier attempts at using Python for this. Add Answer. Question Tools Follow. Powered by Askbot version 0. Please note: ROS Answers requires javascript to work properly, please enable javascript in your browser, here is how.

Ask Your Question.I haven't experimented much here and I'll update this when I do try it tomorrow, but it seems like the documentation says only the other direction is possible: values can be set on the parameter server from within a launch file, and the local copies of those values can be used inside that same launch file and used as arguments, but there is no read access to the parameter server?

I'm not sure this is possible. You may get better answers if you elaborate on why you want to do this. I'd like to have a centralized place the yaml file defining critical robot dimensions, then pass these into a xacro file defining the robot, but also allow certain nodes to get some of the same dimensions from the parameter server.

You can do some pretty complex things with this, especially when you combine it with the other new features xacro gained. I hadn't heard about that so I'm now subscribed to the xacro wiki page. I don't know. Both have their dis advantages.

I think the better solution here is for any node that needs the dimensions of the robot should pull them from the URDF that's already on the parameter server, or from one of the static transforms that's published based on the URDF. I agree.

ruamel.yaml (yaml 1.2)

Traversing the urdf data structure to find a dimension seems like a lot of work compared to using the input dimension from the source. It can be an error check to define a value, create something from it, and then measure it again as opposed to using the original. Please start posting anonymously - your entry will be published after you log in or create a new account.

Asked: Parse error when using a xacro property loaded through a yaml file. Is there a package which allows you to convert. First time here? Check out the FAQ! Hi there! Please sign in help. How to pass parameters loaded from a yaml file into a xacro?See Footnotes.

See How to Disable the Warning below. That means it could call any system command using os. Here is a trivial example:. YAML is cross-programming language, data serialization language. Pickle is Python's native binary data serialization format. Pickle is also unsafe, and documented loudly as such. There are 4 loaders to choose from. See Below The load function was also made much safer by disallowing the execution of arbitrary functions by the default loader FullLoader.

If you are simply using Python software that issues the "load deprecation" warning, you should notify the authors of that software about it, so they can make and release the proper adjustments. Loads the full YAML language. Avoids arbitrary code execution. Make sure they are aware of the warning.

Then you can "globally" disable the warning with:. This page will be kept up to date with the latest information about the load deprecation, usage and warnings. Skip to content. PyYAML yaml. Here is a trivial example: python -c 'import yaml; yaml. How to Disable the Warning If you are simply using Python software that issues the "load deprecation" warning, you should notify the authors of that software about it, so they can make and release the proper adjustments.

This is recommended for loading untrusted input. UnsafeLoader also called Loader for backwards compatability The original Loader code that could be easily exploitable by untrusted data input. You may also use one of the shortcut "sugar" methods: yaml. Then you can "globally" disable the warning with: yaml.

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